Note 11 - Fair Value of Financial Instruments - Quantitative Information About Recurring Level 3 Fair Value of Financial Instruments (Details) $ in Thousands	Sep. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Securities available for sale, fair value	$ 825,475	$ 822,655
Valuation Technique, Discounted Cash Flow [Member] \| Junior Subordinated Debentures [Member]
Borrowings	$ 43,910	$ 41,849
Valuation Technique, Discounted Cash Flow [Member] \| Weighted Average [Member] \| Measurement Input, Discount Rate [Member] \| Junior Subordinated Debentures [Member]
Liabilities, Weighted average	0.042	0.049
Trust Preferred Securities [Member] \| Valuation Technique, Discounted Cash Flow [Member]
Securities available for sale, fair value	$ 1,318	$ 1,256
Trust Preferred Securities [Member] \| Valuation Technique, Discounted Cash Flow [Member] \| Weighted Average [Member] \| Measurement Input, Discount Rate [Member]
Assets, Weighted average	0.042	0.049

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118954083&loc=d3e26610-111562

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-Publisher FASB
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-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
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Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611

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Value of input used to measure debt instrument, including, but not limited to, convertible and non-convertible debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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